1. Field of the Invention
This invention relates to a process for preparing polyolefins using a novel polymerization catalyst. More particularly, it is concerned with a process for preparing polyolefins which comprises making at least one compound selected from the group consisting of a titanium compound and a vanadium compound which are a component of Ziegler catalyst, supported on a carrier, said carrier being composed of a product obtained by treatment with SO.sub.3 of at least one member selected from the group consisting of an oxide and a double oxide of Group II-IV metals of the Periodic Table, thereafter activating said compound supported on said carrier with an organometallic compound, and polymerizing or copolymerizing olefins using the resulting catalyst.
2. Description of the Prior Art
In the technical field of this sort there has heretofore been known a catalyst comprising a transition metal compound such as titanium and vanadium compounds supported on various kinds of inorganic solids as a carrier. As typical of these inorganic carriers are mentioned, for example, alumina, titanium dioxide, zirconia, silica, thoria, and magnesia (see Japanese patent publication No. 25353/1969).
In general, however, those catalysts obtained by supporting a transition metal compound such as a titanium compound and/or a vanadium compound which are a component of Ziegler catalyst on the above-mentioned carriers, and subsequently activating said transition metal compound supported on said carrier with an organo-metallic compound, have a low activity and thus they are disadvantageous in this point. Among the above-mentioned carriers, magnesia has been known to afford a relatively high activity, but alumina and silica have afforded nothing but catalysts of an extremely low activity.
On the other hand in the process for preparing polyolefins it is desirable that polymerization activity be as high as possible. If the polymerization activity is high, it is possible to obtain polyolefins in high hield at a low partial pressure of monomer and that in a short period of time, with the cost of catalyst being of course reduced; in addition, the step of removing catalyst, which step is usually required, becomes simpler and, in some cases, even if the step of removing catalyst is omitted, the resulting polymer can sufficiently be put to practical use, with an extremely low amount of ash content remained in the polymer. As a result, there is provided a process for preparing polyolefins, which process, as a whole, is extremely simplified. From this point of view, many of the catalyst systems using the above-mentioned inorganic carriers as they are have a low activity, and it has been considered necessary that they should be improved.